1. Field of the Invention
The present invention relates to transducers. More specifically, the present invention is directed to a signal correction circuit for a transducer output signal.
2. Description of the Prior Art
Many of the transducers or sensors used in industrial process control to monitor various process variables, e.g., temperatures, pressure, etc., produce output signals which are not directly usable, e.g., they may be non-linear, and, hence, must be linearized before being used to provide an associated process control system to produce control functions for the industrial process being monitored. Examples of prior art sensor signal correction circuits include linearization circuits for linearizing outputs of such non-linear transducers by having the linearizing circuit operating on the actual sensor output signal to convert it to a linearized value as is shown in U.S. Pat. No. 3,748,446 and by using stored tables of linearized sensor output on information which is selectively read-out substituted for the transducer output signal as shown in U.S. Pat. No. 2,987,704. The major problem associated with such prior art structures is the lack of specific correlation directly between the linearization information and the transducer. For example, the information stored in a look-up table in a memory device, e.g., magnetic drum, random access memory, etc., is not directly physically related to a particular transducer and may be incorrectly associated with a transducer particularly when the transducer is replaced. Accordingly, it would be advantageous to have such characterizating, or correction, information stored or physically located with the transducer whereby the information is always physically correlated to the particular transducer and is automatically changed when the transducer is replaced. However, to store the aforesaid look-up table data storage type of apparatus as shown in the aforesaid prior art within the physical structure of the transducer is basically impractical owing to the lack of physical space available and the number of electrical connections to be made between such a combined structure and an external monitoring system, which may include a digital computer, would be physically and economically unfeasible. Finally, such a combined system would require a large power supply or power input in order to energize the components of such a data storage system even if such a system could somehow be accommodated within a greatly enlarged sensor housing. Accordingly, it would be advantageous to provide a system for storing characterizing information for a sensor which is compatible with the internal space normally associated with the sensor housing and which requires only a minimum of electrical connections and power input thereto.